256 Studies in the Theory of Descent. 

 PTEROGON CENOTHER^E, FABR. 



The adult larva, as made known by many, and 

 for the most part good figures, has very complicated 

 markings, which do not seem derivable from any 

 of the elements of marking in the Sphingidce 

 hitherto considered. I was therefore much sur- 

 prised at finding a young caterpillar of this 

 species, only twelve millimeters in length, of 

 a light green colour, without any trace of the 

 subsequent latticed marking, and with a broad 

 white subdorsal line extending along all the twelve 

 segments. (PI. VII., Fig. 63). Judging from the 

 size and subsequent development, this caterpillar 

 was probably in the third stage. 



The same colouring and marking remained 

 during the following (fourth) stage ; but in the 

 position occupied by the caudal horn in other 

 Sphingidcz, there could now be observed the rudi- 

 ment of a future ocellus in the form of a round 

 yellowish spot (PL VII., Fig. 64). The subdorsal 

 line disappears suddenly in the fifth stage, when 

 the larva becomes dark green (rarely) or blackish 

 brown ; the latticed marking and the small oblique 

 stripes are also acquired, together with the beauti- 

 fully developed eye-spots, consisting of a yellow 

 mirror with black nucleus and ground-area (PL 

 VII., Fig. 65). 



The North American Pterogon Gaurcz and P. 

 Abboti^ also show markings precisely similar to 



47 [These species = Thyreus Abbott and Proserpinus Gaurce 



